It is known that in vector control of a polyphase AC motor, high-frequency components become superimposed on the fundamental wave component of the phase current, due to non-uniformity of magnetization of the rotor magnet constituting the AC motor and due to the shapes of the rotor and the stator. For example in the case of the AC motor disclosed in Patent Literature 1 (PTL 1), high-frequency components of the actual current are converted to direct current by high-order dq transformation, and feedback control is executed on a high-order current command value that is set as zero.